As a recording medium for use as a backup for a computer memory, there has been known a magnetic tape cartridge comprising a magnetic tape wound around a single reel and a flat cartridge casing which is formed of square upper and lower casing halves fastened together and in which the reel is housed for rotation.
Since the magnetic tape is used for storing important information, the magnetic tape cartridge is structured so that trouble such as tape jam does not occur and the magnetic tape is not accidentally drawn out.
A leader member (e.g., a leader pin) is fixed to the leading end of the magnetic tape and the recording and reproducing apparatus is arranged to catch the leader member to draw out the magnetic tape from the magnetic tape cartridge to a position where information recorded on the tape can be read out and information can be recorded on the tape. The leader pin is removably held on the cartridge casing. It is advantageous for the purpose of simplification of the structure to hold the leader on the cartridge casing by use of a spring member.
When a leader pin is employed as the leader member, the leader pin generally comprises a central shaft portion to which the leading end portion of the magnetic tape is fixed, a pair of thin shaft portions formed on opposite ends of the central shaft portion, and a pair of head portions which formed on outer sides of the thin shaft portions and is of substantially the same diameter as the central shaft portion. The thin shaft portions form engagement portions which are brought into engagement with a tape draw-out mechanism of a recording and reproducing apparatus when the magnetic tape cartridge is loaded in the recording and reproducing apparatus. The head portions on opposite ends of the leader pin are brought into engagement with leader pin holding recesses formed in the upper and lower casing halves inside the tape draw-out opening. A spring member formed of a plate spring or the like resiliently abuts against the outer peripheral surfaces of the head portions sideway and removably holds the leader pin in the leader pin holding recesses with the axial direction of the leader pin directed in the vertical direction.
The tape draw-out mechanism of the recording and reproducing apparatus is arranged on the assumption that the lower end of the leader pin is located at a predetermined distance from the lower surface of the magnetic tape cartridge, i.e., the bottom surface of the lower casing half of the cartridge casing. That is, it necessary that the leader pin received in the cartridge casing should be constantly held in place in the axial direction thereof.
However, to nullify clearances above and below the leader pin in the leader pin receiving portion is impossible due to limitation in processing accuracy and/or assembling accuracy of the cartridge casing, and is very difficult due to limitation in accuracy of the recording and reproducing apparatus. Accordingly, there exist clearances above and below the leader pin in the cartridge casing, and the leader pin can be displaced from the correct position in its axial direction due to inaccuracy when the leader pin is inserted, and/or to drop impact or vibration during transportation or handling of the magnetic tape cartridge.
In order to overcome these problems, a first object of the present invention is to provide a leader pin locating structure which can confine downward the leader pin held in the cartridge casing.
When the leader pin is taken out from the cartridge casing by the tape draw-out mechanism of the recording and reproducing apparatus, and when the leader pin is returned to the cartridge casing by the tape draw-out mechanism, a part of the spring member is deformed in response to movement of the leader pin. Especially when the spring member is of a plate spring, the edge of the deformed part can scratch the inner surface of the cartridge casing to increase frictional resistance. The increased frictional resistance changes load on the spring member and makes instable the action of the spring member. At the worst, the spring member can be caught by the inner surface of the cartridge casing, and the leader pin can be disabled from being taken out from and received in the cartridge casing.
Further, when the edge of the spring member of metal scratches the inner surface of the casing every time the leader pin is taken in and out the cartridge casing by the tape draw-out mechanism of the recording and reproducing apparatus, the inner surface of the cartridge casing is scraped and shavings can adhere to the surface of the magnetic tape to cause drop out.
Thus a second object of the present invention is to provide a spring member mounting structure which can stabilize the action of the spring member for holding the end portion of the leader pin and can prevents the inner surface of the cartridge casing from being scraped.
Further, the spring member for holding the end portion of the leader pin is required to be simple in structure, to be able to surely hold the leader pin and to be able to be easily incorporated in the cartridge casing.
Accordingly, a third object of the present invention is to provide a spring member which meets such requirements.
The leader pin is required to be simple in structure, to be able to surely and easily clamp the leading end portion of the magnetic tape, and keeps strong clamping force irrespective of environment.
Accordingly, a fourth object of the present invention is to provide a leader pin which can meet such requirements and is provided with a which is less in creep and stress relaxation.
When the leader pin is provided with a clamp member of synthetic resin, injection molding, which can form products of a complicated shape at high efficiency with a high dimensional accuracy, is very useful. However, the injection molding is disadvantageous in that a gate mark projects beyond the surface of the product, which causes a problem in dimensional accuracy.
Thus a fifth object of the present invention is to provide a leader pin having a clamp member whose gate mark is positioned not to adversely affect function of the leader pin.